The thing what killed gunz imo was the v8 update.
First of all it took forever to come out, and when it did come it was so fcking bad.
They ruined all the guns.
They implemented some retarded gem system which gave you more dmg and shit.
I remember logging in to check it out, took me 5 minutes to realise that it was the worst update I've ever seen on this game.
Uninstalled immediately.